<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <button>按钮</button>
  <script>
    // winddow
    setTimeout(()=>{
      console.log("定时器",this);
    },1000) 

    // button
    const btn = document.querySelector('button')
    btn.onclick = function(){
      console.log("按钮点击事件",this);
    }
    btn.addEventListener('click',function(){
      console.log("事件监听",this);
    })

    // window
    const name = ['12',3,4,6]
    name.forEach(()=>{
      console.log('数组循环',this);
    })
  </script>
</body>
</html>